The invention relates to improved image reproduction systems. More particularly, the invention is directed to a data flow control and storage facility for reducing the amount of electronic memory in an image reproduction system.
Electrophotographic copiers, such as digital copiers, are widely used in many business and commercial environments. In a digital copier an input scanning facility captures a document image, and converts the captured image into digital data. A control unit then compresses the image data and either forwards the compressed data to a suitable printing facility, or stores the data in a system memory. System memory typically includes both magnetic disk storage and electronic storage. In conventional systems, electronic storage consists of random access memory (RAM) devices, such as DRAM. The DRAM is used essentially as a page buffer for intermediate storage of image data. To store an 8.5xc3x9711.0 inch image having 600xc3x971200 dots per square inch (dpsi), monochrome applications typically require 8.4 M-bytes of DRAM. Additionally, even relatively low-end copiers require an image data bandwidth of 6 to 7 M-bytes per second. A drawback of storing the image data in DRAM is that it is expensive relative to other, cheaper secondary storage devices, such as a magnetic disk, magnetic tape, optional disk or non-DRAM solid state memories.
To reduce the amount of DRAM required, conventional copiers spool image data from DRAM to magnetic disk memory during scanning. Subsequently, the copier spools the image data from magnetic disk back to DRAM for printing. To facilitate data transfer between DRAM and the magnetic disk memory, conventional high-performance SCSI-based disk subsystems operate disk controllers as bus masters. Operating in master mode, the disk controller can increase the rate with which data is spooled between magnetic disk memory and DRAM. However, even with the above discussed improvements, conventional copiers, nevertheless, continue to employ large amounts of expensive DRAM, and to waste significant time performing spooling operations.
Accordingly, it is an object of the invention to reduce system costs by reducing the amount of DRAM required to operate image reproduction systems.
Another object of the invention is to increase the speed with which image data can be transferred by reducing the number of spooling operations.
The invention will next be described in connection with certain preferred embodiments. However, it should be clear that various changes and modifications can be made by those skilled in the art without departing from the spirit and scope of the invention.
The invention attains the foregoing objects by providing a data flow control and storage facility (hereinafter a xe2x80x9ccontrol and storage facilityxe2x80x9d) for operation within an image reproduction system. According to one embodiment, the control and storage facility includes a digital communication bus, a secondary storage device, an image output controller, an image input controller and a secondary storage controller. The image output controller, image input controller and secondary storage controller are in digital communication over the digital communication bus. Optionally, the secondary storage device and the secondary storage controller communicate by way of an SCSI interface. In a further embodiment, the secondary storage device may be magnetic tape, magnetic disk, optical disk, solid state memory or any other type of digital storage other than DRAM.
The digital communication bus, optionally a PCI-type bus, transfers digital image data in the image reproduction system. The secondary storage device stores the digital image data. The image output controller receives digital image data by way of the digital communication bus and can output the received digital image data to an external destination. The image input controller is adapted for receiving digital image data from an external source and for transferring the received digital image data by way of the digital communication bus.
The secondary storage controller is adapted for transferring digital image data directly from the secondary storage device to the image output controller by way of the digital communication bus. The secondary storage controller is also adapted for transferring digital image data directly from the image input controller to the secondary storage device. Optionally, the secondary storage controller operates in master mode to gain control of the digital communication bus, and transfers blocks of digital image data in a burst format. In a further embodiment, the secondary storage controller includes a buffer cache memory having a write buffer portion and a read buffer portion. The write buffer portion can accumulate a block of digital image data for direct transfer from the image input controller to the secondary storage device. In a similar fashion, the read buffer portion can accumulate a block of digital image data for direct transfer from the secondary storage device to the image input controller. According to one preferred embodiment, the buffer cache memory is a FIFO-type cache memory.
In a further embodiment, the image output controller includes an output cache memory for accumulating a block of digital image data for outputting. Further, the secondary storage controller includes a read master controller. The read master controller determines whether the output cache memory has enough storage available to receive a block of digital image data. In response to determining that enough storage is available, the master controller writes a block of digital image data from the read buffer portion of the buffer cache memory directly to the output cache memory.
Optionally, the read master controller queries the image output controller to determine whether the output cache memory has enough storage available to receive a block of digital image data. Additionally, the image output controller includes output control elements in digital communication with the output cache memory and with the digital communication bus. In response to a query from the read master controller, the output control elements signal the read master controller regarding whether there is enough storage available in the output cache memory to receive a block of digital image data. According to a further embodiment, the output control elements signal a PCI-type disconnect to the read master controller in response to the output cache memory having insufficient storage available.
According to another embodiment of the invention, the image input controller includes an input cache memory for accumulating a block of digital image data for transfer to the write buffer portion of the buffer cache memory. Additionally, the secondary storage controller includes a write master controller for determining whether the input cache memory has accumulated a block of digital image data. In response to determining that a block of digital image data has been accumulated, the write master controller transfers the block of digital image data directly from the input cache memory to the input buffer portion of the buffer cache.
According to a further embodiment, the write master controller signals the image input controller to determine whether the input cache memory has accumulated a block of image data. Additionally, the image output controller includes input control elements in digital communication with the input cache memory and with the digital communication bus. Optionally, in response to the input cache memory not having a block of data accumulated, the input control elements signal the write master controller with a PCI-type disconnect, without transferring any image data.
In an alternative embodiment, the control and storage facility of the invention includes a loop-back channel controller in digital communication with the digital communication bus and adapted for receiving digital image data by way of the digital communication bus and for outputting the received digital image data for additional processing. Additionally, the secondary storage controller is further adapted for transferring digital image data directly to the loop-back channel controller by way of the digital communication bus.
According to additional embodiments, the control and storage facility includes a secondary storage device for storing image data within an image reproduction system; elements for transferring image data from a source external to the control and storage facility to the secondary storage device, without intermediately storing the image data in DRAM; and elements for transferring the image data from the secondary storage device to a destination, external to the control and storage facility, without intermediately storing the image data in a DRAM.
In yet another embodiment, the control and storage facility includes a secondary storage device for storing image data within the image reproduction system; elements for transferring image data, optically scanned into the image reproduction system, into the secondary storage device without intermediately storing the image data in a DRAM buffer; and elements for transferring the image data, stored in the secondary storage device, to an image data output interface of the image reproduction system, without intermediately storing the image data in a DRAM buffer.
According to an alternative embodiment, the invention comprises a method of transferring image data in an image reproduction system. According to one embodiment, the method includes the steps of transferring digital image data from an image input section of the image reproduction system directly to a secondary storage device, without intermediately storing the digital image data in a DRAM buffer; and transferring the image data from the secondary storage device to an image output section of the image reproduction system, without intermediately storing the digital image data in a DRAM buffer.
Thus, the invention provides an improved image data flow control and storage facility, along with related methods, for operation in an image reproduction system. According to the improvements of the invention, image data can be transferred directly from an input interface, such as an optical scanner interface, to a secondary storage device, such as magnetic or optional memory, without intermediately storing the scanned image data in a DRAM buffer. Similarly, the image data can be transferred directly from the secondary storage device to an output interface, such as a printer interface or a supplemental processor interface, also without being stored intermediately in a DRAM buffer.